Chernobyl Nuclear Accident Congressional Hearings Transcript

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Jan Beyea and Frank von Hippel
Containment of a reactor meltdown
Any good scientist or engineer believes
implicitly in Murphy's law: "If
something can go wrong, sooner or
later it will go wrong." The U.S.
Atomic Energy Commission, which
until 1975 had the responsibility for
ensuring the safety of U.S. civilian
power reactors, had many good scientists
and engineers involved in its
work. And during its history it repeatedly
considered the consequences
of all
the safety systems in a nuclear
reactor failing, the fuel melting and
the volatile radioactive isotopes in the
fuel being released to the atmosphere.
The answer which came back from
major studies in 1957 [1], 1965 [2] and
1975 [3] was always that the consequences
could be very serious indeed.
This finding underlined the importance
of preventing nuclear reactor
meltdown accidents. As a result, the
Atomic Energy Commission and the
Nuclear Regulatory Commission
(NRC), its successor in the area of
nuclear safety regulation since 1975,
required so many redundant safety
systems on nuclear power plants that
both nuclear regulators and the
nuclear industry became convinced
that the likelihood of a reactor
meltdown accident had been reduced
to a negligible level.
The massive failure of safety systems
and the associated confusion
which has occurred repeatedly at nu-
Figure 1
LARGE VOLUME PRESSURIZED WATER CONTAINMENT
Figure 2
SMALL VOLUME BOILING WATER CONTAINMENT
CONTAINMENT
HEAT REMOVAL
IfiE COOLANT
SAFETY INJECTION
Because of its large volume {about 60,000 cubic meters), this containment
can hold all of the steam released in the first minutes of a
loss of coolant accident. Subsequently steam pressure should be reduced
by the containment water sprays.
The combined volume of the drj' well and the connected free space
over the pressure suppression pool is only one eiglh that of the containment
shown in Figure I. Steam from the dry well bubbles through
the water in the pressure suppression chamber and is condensed. This
could prevent overpressurization by steam but not by other noncondensable
gases such as hydrogen and carbon dioxide.
Source: T.J. Thompson and J.G. Beckerly. The Technology of Nuclear Reactor Safety, vol. 2, chap. 21 (Cambridge, Mass.: MIT Press, 1973).
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